Radio Frequency (RF) circuits/components (e.g., antennas) are generally made of copper. Copper is inexpensive, it is plentiful, and it has fairly high conductivity and very low resistivity. In the antenna context, resistivity keeps the energy from being radiated out. The energy gets turned into heat instead, thereby lowering the efficiency of the antenna.
Copper is useful for most components where the component size is roughly the size of the natural resonance, which usually occurs at λ/4 or λ/2 or λ, where λ is a wavelength. However, as the size of a component decreases relative to its operating wavelength, resistivity increases greatly. Examples of such components include loaded antennas, such as helix antennas, which decrease the size of an antenna usually to a third or less of its resonant length.
Superconducting materials do not have resistivity (at least when the temperature of the materials drops below critical temperature, Tc). In theory, a superconducting component can provide a much higher efficiency than an all-copper component. Superconducting materials have detriments that make them less than optimal for some deployments. First, they are very expensive. Second, they require a cryogen to provide cooling down to Tc, e.g., Tc of some high-temperature superconductors is 92° K, and is lower for other superconductors, such as low-temperature superconductors. Third, superconducting materials are typically brittle, and it is difficult to shape superconducting materials into anything other than two-dimensional (2D) thin, flat tape or wire.
Currently there are prior art RF systems that employ superconducting materials. One example is solutions that make an entire system out of superconducting materials. Such systems are usually constricted to a 2D surface, take up a large space, and are expensive. Recently, as wireless base stations become more complicated, engineers are facing heat issues, particularly with power amplifiers and filters. In the commercial area people are beginning to use filters made of superconducting materials for outdoor base stations, and the cost goes up because of the material and the cryogenic cooling system. However, the space requirements are reduced significantly, which can offset the increased cost of manufacture. One base station system uses filters that are completely made of superconducting material.
Another prior art system includes a filter bank with some filters made of superconducting materials and other filters made of non-superconducting materials. Yet another prior art system includes a copper antenna embedded in a superconducting sphere or column to improve the antenna fields after they have left the antenna and before they go out into free space, similar to a lens effect. However, these prior art systems that employ whole circuits or components made entirely of superconducting materials are hard to build because of the brittleness of superconducting materials, and are expensive to manufacture because of the high cost of superconducting materials.